The physiological actions of parathyroid hormone (PTH) and calcitonin (CT) on kidney and bone are mediated by cyclic 3'5'-adenosine monophosphate (35AMP). The response to PTH and CT of these tissues is affected by several factors, including thyroid and estrogen status, and drugs, such as the benzothiadiazine diuretics. The proposed studies explore the possibility that the interaction of these factors with the end-organ response to PTH and CT is at the level of generation and metabolism of 35AMP. The parameters to be examined include the adenylate cyclase and cyclic nucleotide phosphodiesterase activities from kidney and bone, and the tissue content of 35AMP, measured by a competitive protein-binding assay. Tissue will be obtained from normal, hypothyroid, hyperthyroid, estrogen deficient, or estrogen treated rats. Calvaria will be incubated in vitro and the 35AMP responses to PTH and CT will be measured and compared, one treatment group to the next. Similarly, the adenylate cyclase and phosphodiesterase activities of homogenates of kidney and bone from the various treatment groups will be evaluated. The direct effect of thyroid hormone, estrogen, and thiazide diuretics on these parameters from normal bone and kidney will also be examined. The action of 35AMP appears to require binding of the nucleotide to intracellular receptors as the initial event. These receptors have been isolated from a variety of tissues and have been shown to be proteins possessive of kinase activity. As a corollary study the 35AMP- binding kinase complex from bone will be isolated and characterized.